Tufted carpets are commonly made by inserting tufts of wool, or other yarns, into a backing to form a closely spaced array. A series of needles are used for this purpose, and each needle inserts a row of tufts into the backing as the backing is drawn away from the needle. If one of the needles stops tufting for some reason, for instance if the yarn breaks, then the tufting operation is not stopped but is allowed to continue leaving an empty row in the carpet. Subsequently a hand-held tufting gun is used to insert the missing row of tufts.
The hand-held tufting guns developed for the repair of carpets have been imaginatively applied to the creation of individualised carpets bearing complex and unusual designs; in these carpets it should be appreciated that the tufting is not restricted to straight rows. However, the production of such carpets is a highly labour intensive process and requires great skill and flair on the part of the operator. For instance, the stitch length is determined by a combination of the speed at which the operator traverses the gun across the backing and the speed at which the operator drives the tufting motion of the gun. It is also difficult to traverse the gun accurately across the backing because the action of the gun on the backing introduces forces which deflect the needle.
The hand-held tufting guns include tufting head mechanisms which typically include a reciprocally mounted hollow needle and a yarn feeding mechanism. There are two main types of tufting heads.
First, a purely mechanical type in which a forked rod, or narrow scissors, reciprocates within the hollow needle to drive the yarn into position once the backing has been parted by the needle.
Second, a pneumatic tufting head which uses a stream of compressed air flowing down through the hollow needle to entrain the yarn and drive it into position in the backing.
Both types of tufting guns are subject to a variety of problems in operation, such as yarn blockages, or yarn being blown back out of the needle. These problems make the use of tufting guns difficult to automate.
One attempt at an automated tufting gun is described in U.S. Pat. No. 4,109,593. Here a pneumatic tufting gun is mounted on a carriage movable in two orthogonal directions, and the problem of maintaining the correct orientation of the needle with respect to the direction of traverse is addressed. However, there are still a large number of problems to be overcome before such a device is able to produce an adequate product.